Nickel plating



E. J. Rol-:HL 2,504,239

April 1s, 195o NICKEL PLATING Filed lay 28, 1946 rrd/M/Ey Patented Apr.18, 1.950

NICKEL PLATING Edward Judson Roehl, Little Silver, N. J., assigner toThe International Nickel Company, Inc., New York, N. Y., a corporationof Delaware Application May 28, 1946, Serial No. 672,835 In Canada April12, 1946 2 Claims.

The present invention relates to electrolytic nickel anodes and a methodfor eleetrodepositing nickel employing electrolytic nickelV anodes. Moreparticularly, the present invention relates to welded electrolyticnickel anodes and a method for electrodepositing nickel employing suchwelded anodes.

Heretofore, one of the factors preventing the more extensive use ofelectrolytic nickel for anodes, when employed for electrodepositingnickel from chloride-bearing nickel plating baths, has been that ofpreferential corrosion of weld metals employedin electrolytic nickelanodes. Thus, diculty has been encountered with Weld metals used inwelding together lengths or parts of electrolytic nickel to provideanodes that exceed in length the generally available electrolytic nickelstock. Similarly, difficulty has been encountered with weld metalsemployed in welding together pieces of electrolytic nickel to provideanodes having some particular or desired configuration, as the weldmetals hereinbefore employed have. been found to corrode preferentiallyoften resulting in severance of the anodes along the weld joint orjoints.

Many proposals and attempts have been made to solve the problem ofpreferential corrosion of welds in electrolytic nickel anodes. Forexample, in Canadian Patent No. 392,783, it is proposed to prepare ananode by connecting together several pieces of electrolytic nickel bymeans of a dove-tailed joint protected against electrolytic attack by arubber band covering the joint. This method has not proved to beentirely satisfactory because the anode eorrodes preferentially due toan increase in current density at the edges of the rubber band therebyeventually causing the\ anode to be severed along one edge of the rubberband. When severance of theanode occurs, such as by preferentialcorrosion of the weld joint or joints, the portion of the anode belowthe line of severance drops to the bottom of the bath thereby greatlydiminishing the amount of anode remaining for further plating.Theportion of the anode that drops results in a substantial economicloss and possible damage to the work in progress. Furthermore, if ananode bag is employed, the dropping of the severed portion of the anodeoften ruptures the bag releasing particles enclosed therein into theplating bath thereby adversely affecting the deposit 'on the cathode dueto the physical inclusion of the particles in the deposit.

As will be readily appreciated from the foregoing, there is a wellrecognized need in the art of nickel electroplating for a weldedelectrolytic nickel anode and a method for electrodepositing nickelemploying a welded electrolytic nickel anode, whereby the weldedelectrolytic nickel anode does not exhibit preferential corrosion of 1 2the weld joint or joints when the weld metal is in contact with theelectrolytic nickel of the anode proper and the anode is subjected tothe, electrolytic and/or corrosive eiects of a chloridebearing nickelelectro-plating bath. As far as I am aware, the proposals and attemptsthat have been made heretoforeA in an endeavor to overcome the foregoingand other difficulties. and problems have not been completelysatisfactory. when carried into practice, in overcoming the obstacle ofpreferential corrosionJ I have discovered that undesirable preferential,

corrosion of a dissimilar metal composition, as

for example, a welded joint or joints in an electrolytic nickel anode,when employed in electrodepositing nickel from a chloride-bearing bath.is overcome when the dissimilar metal composition comprises a nickelweld such as the compositions hereinafter described, and the weldedelectrolytic nickel anode is employed in electrodepositing nickel froman aqueous bath operated under correlated conditions of`pH and chloridenormality.

/It is an object of the present invention to provide a method wherebywelded electrolytic nickel anodes may be employed without exhibitingpreferential corrosion of the weld joint or joints in electrodepositingnickel from a chloridebearing plating bath.

It is another object of the present invention to provide a method forelectrodepositing nickel employing a welded electrolytic nickel anodeand a bath operated under correlated conditions of pH and chloridenormality whereby the weld metal ycomposition in contact with theelectrolytic nickel of the anode proper does not exhibit preferentialcorrosion with respect tothe electrolytic nickel. 1

It is a further object of the present invention to provide a weldedelectrolytic nickel anode in which the weld metal does notpreferentially corrode when subjected in contact with the electrolyticnickel ofi-thev anode proper to the electrolytic, corrosive and/or otherdetrimental eects of a chloride-bearing nickel electro-plating bath, andto provide a method for producing such welded electrolytic nickelanodes.

It is another object of the present invention to provide an elongatednickel anode by weldingI together members of electrolytic nickel wherebythe anode does not exhibit preferential corrosion of the weld joint orjoints when the anode is subjected to the electrolytic, corrosive and/orother detrimental action of a chloride-bearing nickel electroplatingbath and to provide a method for producing such an elongatedelectrolytic nickel anode.

It is also within the purview of the present invention toprovide weldedelectrolytic nickel anodes shaped to conform approximately with thecathode, which anodes do not exhibit prefer-` ential corrosion at theweld jointor joints when subjected to the electrolytic, corrosive and/orother detrimental action of a chloride-bearing nickel electro-platingbath and to provide a method for producing such electrolytic nickelanodes.

Various other objects, advantages and features of the present inventionwill become apparent from the following detailed description when takenin conjunction with the accompanying drawings in which:

Fig. 1 illustrates an elongated, welded, electrolytic nickel anodeprepared in accordance with the present invention;

Fig. 2 is a welded electrolytic nickel anode hav ing an irregular shapeprepared in accordance with the present invention; Fig. 3 represents achart showing chloride normality as abscissa plotted against pHasordinate, showing the area for correlation of pH and chloride normalityfor plating baths whereby the weld metal joint or joints of theelectrolytic nickel anodes prepared in accordance with the presentinvention do not exhibit preferential corrosion: and

Fig. 4 depicts curves showing anode potentials for electrolytic nickeland the weld metal compositions employed in preparing an anode such asemployed in practicing the present invention.

Generally speaking, the present invention provides a method forelectrodepositing nickel, employing an electrolytic nickel anode havingat least one nickel weld joint, from a chloride-bearing nickelelectro-plating bath operated under correlated conditions of ,pH andchloride normality whereby the weld metal does not exhibit preferentialcorrosion with respect to the electrolytic nickel of the anode proper.The present invention also provides a welded electrolytic nickel anode,comprising a weld metal composition dissimilar to the electrolyticnickel of the anode proper, and in contact therewith, which dissimilarcomposition does not exhibit preferential corrosion when subjected tothe electrolytic, corrosive and/or other detrimental action of achloride-bearing nickel plating bath in electroplating therefrom.

For the purpose of obtaining satisfactory re sults by practicing theprocess of the present A invention in electrodepositing nickel fromchloride-bearing baths employing welded electrolytic nickel anodes, anickel weld metal is employed for welding the electrolytic nickel anode.I have found that the generally available type of nickel weld metals,particularly nickel weld metals con taining at least about 90% nickeland preferably at least about 97% nickel are suitable when employed inwelding electrolytic nickel anodes whereby the weld joint or joints donot preferentially corrode when subjected in'contact with theelectrolytic nickel of the anode proper to the electrolytic and/orcorrosive effects of a chloridebearing plating bath correlated in pH andchloride normality as hereinafter described. As is well known to thoseskilled in the art, nickel weld metals contain modifying ingredients, inaddition to their nickelcontent, in order that the weld metalcomposition will perform satisfactorily in weld operations. Examples ofsuch ingredients are aluminum and silicon as deoxidizers to promote weldsoundness, titanium as a deoxidizer to promote weld soundness and toprevent hot shortness and as a stabilizer for arc welds. magnesium topromote hot ductility by xing Nickel Silicon sulfur, .carbon to promoteweld soundness and as described.

Element Percent Silicon 0.1 to 2.0 Carbon 0 03 to 1.3 Titanium 0. 05 to2.0 Aluminum.... 0.0 to 2.0 Manganese 0.0 to2 0 Magnesium 0. 04 toO l2Nickel Balance While the composition given hereinbefore has been foundsatisfactory for welding the electrolytic nickel anodes, in carrying thepresent lnvention into practice, I prefer to employ a weld metalcomposition such as the following containing about 97%` nickel:

Element Percent Carbon Titanium Aluminum.. Manganese.. Magnesium.

Bula c more than about 0.2% of minor constituents, im-

purities and incidental elements may be present, replacing an equivalentamount of the nickel content. Although the presence of these minorconstituents is not essential for obtaining the improved results f thepresent invention, these minor constituents are generally found to bepresent as unavoidable impurities in the production of available nickelwelds. Examples of such un avoidable impurities are iron, copper, sulfurand cobalt.

In producing a welded electrolytic nickel anode, I havev found that whenthe weld metal employed comprisesthe compositions .hereinbeforeAdescribed, the welded anode does not exhibit preferential corrosion ofthe weld joint or joints when the weld metal is in contact with theelectrolytic nickel of the anode proper and the anode is subjected tothe electrolytic and/or corrosive effects of a chloride-bearing nickelplating bath having the pH and chloride normality correlated ashereinafter described.

Referring to the drawings, Fig. 1 illustrates an elongated nickel anode,such as embodied by the present invention, prepared by welding togethermembers of electrolytic nickel with a nickel weld of the compositionshereinbefore set forth. As shown in Fig. 1, twomembers of electrolyticnickel. designated by reference character I0, are welded together atweld H with the nickel weld metal composition employed by the present`jected in contact. with the 'electrolytic nickel of.

electrolytic nickel anode may comprise several such as shown bly-Fig. 1.has been found to perform satisfactorily in the process of the presentinvention hereinafter described, in that the weld metal does notpreferentially corrode when sub- 5 the anode to the eilects of achloride-bearing, nickel electroplating bath maintained under correlatedconditions of pH and. chloride normality.

Furthermore, as shown in Fig. 2, the present l invention is,` applicableto provide electrolytic nickel anodes having an irregular shape; forexample, a 'shape conforming approximately to that of the cathode. Suchlanodes are desired for use in the plating of articles which them- Nlselves have an irregular shape whereby the effect of current densityupon the surface* of the article to be plated is equalized and thethrowing power increased. As illustrated in F18. 2, the

differently shaped members -of electrolytic nickel designated byreference numerals Il and il. As shown, members I2 and il are jointedtogether at welds i4 with the hereinbefore described weld metalcompositions. "In this manner, electrolytic nickel anodes are providedwhich do not exhibit preferential corrosion at the weld joint or jointswhen employed ircontact with the electrolytic nickel of the anode to theelectrolytic and/or. corrosive effects of a chloride-bearing nickelelectro-plating bath maintained under correlated conditions of pH andchloride normality.

I have found that in electrodepositing nickel from a chloride-bearingbath, electrolytic nickel anodes prepared as hereinbefore described donot exhibit preferential corrosion at the weld Joint or joints when theelectrodeposition is carried out yfrom a bath maintained undercorrelated conditions of pH and chloride normality. The conditions forcorrelation of pH and chloride normality of the electrogplating bathinorder to .obtain the results contemplated by the present invention, i.e., whereby the weld metal does not preferentially corrode,are clearlyshown by reference to Fig. 3 in which' chloride normalityas abscissa isplotted against pH as ordinate. I have found that in electrodepositingnickel from a chloride-bearing bath, and employing welded electrolyticnickel anodes vprepared as hereinbefore described, the weld metal doesnot pref- '50 ereltially corrode when the plating bath is maintainedunder conditions of pH and chloride normality falling in the area undercurve A of Fig. 3.

Curve A of Fig. 3 showsthe approximate maximum pH which should beemployed for the bath, correlated with the chloride normality of thebath, in ordere that the weld joint or joints will not preferentiallycorrode. Thus, as will be observed by reference to F153, when a nickelelectro-plating bath having a chloride normality of about 0.4 isemployed, the maximum pH for preventing preferentiall corrosion of theweld is about pH 2.0. Similarly, for a bath having a chloride normalityof about 1.0, the maximum pH is about 3.5, and for a bath having achloride normality of about 2.8, the maximum pH is about 4. Hence. aswill be appreciated by those skilled in the art, it is a simple matterwhen the pH oi' the chloride normality of a bath is known, to refer toFig. 3 and correlate pH and chloride normality of the nickelelectroplating bath to fall under the area defined by curve A andthereby the electrolytic nickel anodes prepared as herecurve A of Fig.3.

inbefore described does not preferentially cor-'- .rodewith respect tothe electrolytic nickel of the anode proper.

In determining the necessary correlation ofv pH umd chloride normalityfor operation of the e chloride-bearing baths, whereby. the weld metalof the electrolytic nickel anodes is not preferentially corroded, nickelplating baths of varying compositions were employed. Among the aqueousplatingbaths used were those having the followin g compositions:

In practicing the present invention, the temperature of theelectro-plating bath may be varied over a wide range of temperature,such as from about F. to the boiling point of the bath. However, forbest results, I preferto employ a bath temperature of F. to 140 F., i.e. about F.

With reference to current density, a wide range of current density,- maybe employed in practicing the present invention and the desired resultscontemplated obtained; i. e., that the weld joint or joints of theelectrolytic nickel anodes do not preferentially corrode when employedin electro- .depositing nickel from a bath correlated in pH landchloride normality to fall in the area under Thus, for example, anodecurrent densities of 30. and 100 ampersper square foot have been foundsatisfactory for electrodepositing nickel from baths having-chloridenormalities and pH correlated to fall in the area under curve A of Fig.3. I have found 'that current densities lower than 30 amperes per squarefoot and higher than about 100 amperes per square foot may also beemployed with satisfactory results in electrodepositing nickel frombaths correlated in pH and chloride normality as hereinbefore set forth.The current densities of 30 and 100 amperes per square foot are setforth merely to show that the present invention is applicable to a 'widerange of current density and particularly for current densitiesgenerally employed in large scale commercial nickelelectroplatingsoperations.

. For the purpose of giving those skilled in the art a betterunderstanding of the present invention and the improved results obtainedthereby, the following illustrative examples are given:

Example I An electrolytic nickel anode was prepared by welding togetherpieces of electrolytic nickel with a weld metal having thefollowing'composition:

The `welded electrolytic nickel anode was used as an anode in an aqueousnickel electroplating bath containing 300 grams per liter of nickelsulfate,'45 grams per liter of nickel chloride and 30 grams per liter ofboric acid. The chloride normality of the bath was about 0.4. At a bathtemperature of about 130 F. and. employingl an anode current density ofabout 30 amperes per i square foot, it was found that the weld did notwelding together pieces of electrolytic nickel with a weld metal havingthe following composition:

Element Percent Manganese Magnesium.. Nickel Bala The weldedAelectrolytic nickel anode was used as an anode in an aqueous nickelelectroplating bath containing 285 grams per liter of nickel sulfate,112 grams per liter of nickel chloride and 40 grains per liter of boricacid. The chloride normality ofthe bath was about 1.0. At a bathtemperature of about 130 F. and by employing an, anode current densityof about amperes per square foot, it was found that the weld metal didnot corrode preferentially with respect to the electrolytic nickel ofthe anode when the pH of the bath did not exceed about 3.5, but that theweld metal corroded preferentiallywhen a pH of l,about 3.5 was exceeded.

\ Example III An electro/lyticnickel anode was prepared by weldingtogether pieces of electrolytic nickel with a weld metal having thefollowing composition:

Element Percent Silicon 0. l to 2. 0 Carbon. 0. 03 to l. 8 Titanium.- 0.05 t0 2.0 Aluminum... 0 to 2. 0 Manganese.A 0 to 2.0 Magnesium.. 0.04 to0.12 Nickel Blan The welded electrolytic nickel anode was employed as ananode in an aqueous nickel electroplating bath containingv 29 grams perliter of nickel sulfate, 330 grams per liter of nickel chloride and 40grams per liter of boric acid. The chloride normality of the bath wasabout 2.8. At a bath temperature of 130 F. and employing an anodecurrent density of about 30 amperes per square foot, it was found thatthe weld metal did not corrode preferentially when the path pH did notexceed about 4.0 whereas at a pH exceeding about 4.0, the weld metalcorroded preferentially.

Although the exact nature of the phenomena,

. explaining vthe improved resistance to preferenbe helpful inunderstandingthe principles underlying the present invention.

In the welding of nickel anodes, as proposed by the prior art, it isbelieved that preferential the current density effective thereon ishigher than on theelectrolytlc nickel of the anode and preferentialcorrosion is exhibited by the weld metal when in contact withelectrolytic nickel of the anode and subjected to the electrolytic,corrosive and/or other detrimental eiects of the plating bath. Byemploying la welded electrolytio nickel anode, prepared in accordancewith the present invention, in a chloride-bearing bath correlated in pHand chloride normality to fall in the area under curve A of Fig, 3, theweld metal has aless active or more noble anode potential than theelectro-nickel of the yanode proper. Thus, the current density effectiveupon the weld metal is less than upon the electrolytic nickel of theanode proper and preferential corrosion of the weld metal does notoccur. In this connection, Fig. 4 is a chart showing anod'e potentialcurves by plotting anode potential in volts versus bath pH for theelectrolytic nickel and the weld metal compositions employed by thepresent invention. The values depicted in Fig. 4, i. e., anode potentialvalues on the saturated calomel scale, were obtained by employing asaturated calomel electrode fitted with a saturated potasslum chloridesalt bridge in series with a plating bath bridge. In Fig. 4, curve Xdesignates the anode potential` curve for the electrolytic nickel of theanode whereas curve Y shows the anode potential curve for the weld metalemployed by the present invention. AsA will be noted from these curves,the anode potential of the weld metal employed by the present inventionis more noble than that for electrolytic nickel. Because the weld metalemployed by the present invention does not corrode preferentially whenin contact with electrolytic nickel and subjected to the electrolyticand/or corrosive effects of a nickel plating bath'correlated in pH andchloride normality as hereinbefore set forth, it is believed that theresistance to preferential corrosion of the weld metal is due to itsmore noble anode potential. By reference to Fig. 4 it will be readilyobserved that the weld metal has a. more noble anode potential thanelectrolytic nickel at a bath pH not exceeding about 3.5 whereas with abath pH exceeding about 3.5, the electrolytic nickel has a more nobleanode potential than the weld metal. Although the believed reasons forthe improved resistance to preferential corrosion exhibited by the weldmetal of the present invention are recited hereinbefore, it is to beunderstood that the theory underlying the improved performance obtainedby practicing the present invention may be different than that recitedhereinbefore. However, regardless of the reasons underlying the improvedresults obtained with the present invention, it has been found thatpreferential corrosion of the weld metal employed by the presentinvention. does not occur when the Weld metal is in contact withelectrolytic nickel of the anode proper and subjected to theelectrolytic, corrosive and/or other detrimental effects of an aqueousnickel plating bath having a chloride normality and pH correlated/tofall under the area defined by curve A in Fig. 3.

The electrolytic nickel employed in preparing the anodes'used in theprocess of the present in- Element Although the present invention hasbeen described in conjunction with certain preferred embodiments, suchas the electrolytic nickel anodes depicted in Figs. 1 and 2, thoseskilled in the art will understand that various modifications thereofmay be made. Thus, generally speaking, it should be understood that thepresent invention is applicable to the Welding of component parts ofelectrolytic nickel anodes that are employed in electrodepositing nickelfrom a chloride-bearing nickel plating bath maintained under correlatedconditions of pH and chloride normality falling in the area dened bycurve A in Fig. 3 of the drawings. Furthermore, although a typicalcomposition of electrolytic nickel, such as obtained fromchloride-containing electrolytes, has been set forth hereinbefore forpreparing the anodes, it should be understood it is not intended tolimit the present invention to the composition set forth as, inpracticing the present invention, the electrolytic nickel compositionsgenerally available to the nickel electro-plating industry for use asanodes may be satisfactorily employed.

I claim: 4

1. 'I'he method oi electrodepositing nickel with a welded electrolyticnickel anode which comprises establishing an aqueous nickelelectroplating bath having a pH up to about 4.0, a chloride normalityoi.' about 0.4 to about 2.8, and a nickel sulfate content correspondingto 300 to 29 grams per liter of NiSO4-7H2O, said pH and chloridenormality being correlated to fall under curve A in the accompanyingFig. 3; immersing in said nickel electroplating bath a weldedelectrolytic nickel anode comprised of a plurality oi' portions ofelectrolytic nickel welded together with at least one nickel Weld metaljoint, said welded anode being so immersed in said bath that said nickelweld metal Joint is exposed in contact with said electrolytic nickel tosaid nickel electroplating bath, said nickel weld metal containing about0.1 to y2% silicon, about 0.03 to 1.3% carbon, about 0.05 to 2%titanium, up to about 2% aluminum, up to about 2% manganese, about 0104to 0.12% magnesium, with the balance essentially nickel constituting atleast 97% of the weld metal. said electrolytic nickel being the typeproduced from a sulfate-chloride electrolyte and containing about 0.001%lead, about 0.001% arsenic, about 0.001% iron, about 0.003% to about0.005% copper, about 0.01% to about 0.1% cobalt, with the balanceessentially nickel; and passing a plating current from said welded anodeto a cathode immersed in said nickel electroplating bath to anodicallycorrode said welded anode without producing preferential corrosion ofsaid nickel weld metal with respect to said electrolytic nickel o1' saidwelded electrolytic nickel anode.

2. The method of electrodepositing nickel with a welded electrolyticnickel anode which comprises establishing an aqueous nickelelectroplating bath having a pH up to about 4.0, a chloride normality ofabout 0.4 to about 2.8, and a nickel sulfate content corresponding to300 to 29 grams per liter of NiSO4'7I-l20, said pH and chloridenormality being correlated to i'all under curve A in the accompanyingFig. 3; immersing in said nickel electroplating bath a weldedelectrolytic nickel anode comprised of a plurality oi portions oi'electrolytic nickel welded together with at least one nickel weld metaljoint, said welded anode being so immersed in said bath that said nickelweld metal `oint is exposed in contact with said electrolytic nickel tosaid nickel electroplating bath, said nickel weld metal containing about0.1 to 2% silicon, about 0.03 to 1.3% carbon, about 0.05 to 2% titanium,up to about 2% aluminum, up to about 2% manganese, about 0.04 to 0.12%magnesium, with the balance essentially nickel, said electrolytic nickelbeing the type produced from a sulfate-chloride electrolyte andcontaining about 0.001% lead, about 0.001%

y arsenic, about 0.001% iron, about 0.003% to about 0.005% copper, about0.01% to about 0.1% cobalt, with the' balance essentially nickel; andpassing a plating current from said welded anode to a cathode immersedin said nickel electroplatlng bath to anodically corrode said weldedanode without producing preferential corrosion of said nickel weld metalwith respect to said electrolytic nickel oi' said welded electrolyticnickel anode. EDWARD JUDSON ROEHL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

1. THE METHOD OF ELECTRODEPOSITING NICKEL WITH A WELDED ELECTROLYTICNICKEL ANODE WHICH COMPRISES ESTABLISHING AN AQUEOUS NICKELELECTROPLATING BATH HAVING A PH UP TO ABOUT 4.0, A CHLORIDE NORMALITY OFABOUT 0.4 TO ABOUT 2.8, AND A NICKEL SULFATE CONTENT CORRESPONDING TO300 TO 29 GRAMS PER LITER OF NISO4$7H2O, SAID PH AND CHLORIDE NORMALITYBEING CORRELATED TO FALL UNDER CURVE A IN THE ACCOMPANYING FIG. 3;IMMERSING IN SAID NICKEL ELECTROPLATING BATH A WELDED ELECTROLYTICNICKEL ANODE COMPRISED OF A PLURALITY OF PORTIONS OF ELECTROLYTIC NICKELWELDED TOGETHER WITH AT LEAST ONE NICKEL WELD METAL JOINT, SAID WELDEDANODE BEING SO IMMERSED IN SAID BATH THAT SAME NICKEL WELD METAL JOINTIS EXPOSED IN CONTACT WITH SAID ELECTROLYTIC NICKEL TO SAID NICKELELECTROPLATING BATH, SAID NICKEL WELD METAL CONTAINING ABOUT 0.1 TO 2%SILICON, ABOUT 0.03 TO 1.3% CARBON, ABOUT 0.05 TO 2% TITANIUM, UP TOABOUT 2% ALUMINUM, UP TO ABOUT 2% MANGANESE,